Phase II Final Report - NASA's Institute for Advanced Concepts

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
Because the wings of the Entomopter are constantly moving during flight, the output of the array
will vary continuously. The total wing motion is 150°, +75° (up from the horizontal), and -75°
(down from the horizontal). The curves in Figures 3-178 and 3-179 represent the output power
of the wing at these three locations. The power output is given as a function of time of day for
one complete day cycle. The total usable power available per stroke is given by the average
power curve. This curve represents the average power available throughout a wing stroke.
The output power for the total array can be obtained by multiplying the power level on the
graphs (11 or 12) by 4. The output is based on a solar intensity of 590 W/m 2 and an atmospheric
attenuation of 15%. The mass of the solar array, based on the CuInSe 2 array, would be 0.014 kg.
As can be seen from Figures 3-173 through 3-177, the available power changes considerably as
the latitude and time of year change. This is due to the inclination of Mars and the change in
incident angle on the array due to the change in latitude. For the data shown, it was assumed that
the Entomopter was flying east to west.
The average output power per wing stroke for the total array (four panels) is shown in Figure 3-
180. The average output power can vary greatly depending on latitude and time of year.
Figure 3-180 represents the extremes in average output power, the equator and near the North
Pole, at the time of summer solstice. The time of year, especially at higher latitudes, can greatly
effect the array output. For example, during the winter at the 85° North latitude there would be
no sunlight and therefore no array output for extended periods of time. The watthours provided
by the solar array for a day period based on the curves shown in Figure 3-180 are as follows:
• Equator at Solstice 55.71 W-h
• 85° North Latitude at Solstice 107.62 W-h
This is the amount of energy available from the solar array for the given day.
3.6.6 Lithium Batteries
The energy storage component of the system will be used to provide power when the solar array
is either obscured from sunlight (either by being shadowed or during nighttime) or when the
power demand is greater than what the array can provide. Presently, lithium polymer batteries
hold the most promise for a lightweight rechargeable system.
Lithium batteries can be configured in virtually any prismatic shape and can presently be made
thinner than 0.039" (1 mm), to fill virtually any space efficiently. This would be a great benefit
in entomopter design, because it allows the battery to be placed almost anywhere in the vehicle.
It also presents the possibility of making the wing the complete power system by having the batteries
within the wing and the solar cells on its surface. One potential lithium battery technology
that may address this application are thin film lithium batteries.
Lithium ion thin film batteries are a relatively new technology that is readily finding applications
in industry and commercial products, including implantable medical devices, remote sensors,
transmitters, smart cards, CMOS-SRAM memory, and other electronic devices. These
batteries are rechargeable, lightweight, and flexible. They can be configured in any series/paral-
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Phase II Final Report